1. Field of the Invention
The present invention relates to a method for producing an ink jet head, an ink jet head produced by the method, and an ink jet apparatus for use of the ink jet head.
2. Related Background Art
A recording apparatus records images (the term "images" herein includes characters) according to image information (the term "image information" herein includes character information or the like) on a recording medium such as paper, a thin plastic film, textiles or any other medium capable of having an image recorded thereon. Such a recording apparatus can function as a printing machine, a copying machine, a facsimile machine and so on, or as an output terminal of a composite electronic machine, such as a work station or the like, functioning as a computer, a word processor and so on. Such a recording apparatus can be characterized by its recording method as an ink jet apparatus, a wire dot apparatus, a thermal printing apparatus, a laser beam apparatus and so on.
In a serial-type recording apparatus using a serial scanning method, in which main scanning is carried out in a main scan direction transverse to a sub-scan direction of conveyance of a recording medium, the recording of images is carried out by a recording means carried on a carriage which moves in the main scan direction along a recording medium after the recording medium is positioned at a predetermined recording region. After recording of one line is finished, a predetermined amount of conveyance of the recording medium in the sub-scan direction is carried out. Then recording of the next line on the stationary recording member is carried out. The main scanning and the sub-scanning are repeated alternately. In this way, recording on the whole recording medium is carried out.
On the other hand, in a full-line type recording apparatus, in which the only movement is the sub-scanning of a recording medium, recording of one line is carried out at almost the same time the recording member is positioned at a predetermined recording region. Then a predetermined amount of conveyance of the recording medium (a pitch of one line) is carried out and recording of the next line is carried out at almost the same time. The one-line recording and the sub-scanning are repeated alternately. In this way, recording of the whole recording medium is carried out. Among the foregoing recording apparatuses, an ink jet recording apparatus carries out recording by discharging ink from a recording head to a recording medium. An ink jet recording apparatus has many advantages. It is relatively easy to produce a compact recording head. Particularly, an ink jet recording head utilizing thermal energy to discharge ink can be made very compact. Images with a high density can be recorded rapidly. Recording on plain paper can be carried out without special treatment of the paper. The running cost is relatively low. Recording can be carried out quietly because it uses a non-impact method. In addition, it is easy to carry out color recording by using plural color inks. An ink jet recording apparatus with a full-line type of recording head which has plural discharge openings extending over the width of a recording area of paper can carry out recording especially rapidly.
In order to carry out ink jet recording of high quality, various methods for producing an ink jet head of high reliability have been proposed. Some of the most effective methods are disclosed in U.S. Pat. No. 4,657,631 and U.S. Pat. No. 5,030,317.
FIGS. 1 to 6 are schematic views showing an example of a method for producing an ink jet head in respect to the aforesaid related background art. In FIGS. 1 to 5, an ink jet recording head with two discharge openings is produced; in FIGS. 6A to 6F more than two discharge openings are formed. However, the example illustrated in FIGS. 1 to 5 corresponds to the example illustrated in FIGS. 6A to 6F.
In this example, as illustrated in FIG. 1, a substrate 1 composed of, for example, glass, ceramic, metal or the like is used as a base member of an ink jet head. FIG. 1 is a schematic perspective view of the substrate on which energy generating bodies for generating energy utilized to discharge ink are provided before formation of ink passages. Numeral 2 designates a energy generating portion of the energy generating body. Electro-thermal converting bodies are used as the energy generating bodies in FIG. 1. However, instead of the electro-thermal converting bodies, for example, piezoelectric elements can be used as the energy generating bodies.
Electrodes (not shown in FIG. 1) for inputting signals are connected to the energy generating portions 2. Functional layers such as a protective layer and the like can be provided with the object of improving the durability of the energy generating bodies.
Next, as illustrated in FIGS. 2A and 2B, a pattern layer 3 is formed according to the pattern of the ink passage on a portion of the substrate 1 on which the energy generating bodies are previously provided. FIG. 2A is a schematic plan view after formation of the pattern layer. FIG. 2B is a schematic cross-sectional view taken along the section line 2B-2B' in FIG. 2A. In this example, for discharging ink from each of two discharge openings corresponding to two energy generating portions of the energy generating bodies, the pattern layer 3 formed on the portion of the substrate 1 comprises parts for two fine ink passages and a part for a common ink chamber for supplying ink to the ink passages.
The material of the pattern layer 3 for this example is a positive type photosensitive material. A positive type photosensitive material has various advantages such as (i) its resolution is better than that of a negative type photosensitive material, (ii) the relief pattern formed thereby has better defined vertical and smooth side wall surfaces, and (iii) the relief pattern formed thereby can be dissolved and removed by using a developing liquid or an organic solvent. Therefore, a positive type photosensitive material is a desirable material for forming the pattern layer 3 as illustrated in FIGS. 2A, 2B and 6A. The positive type photosensitive material may be either a liquid or a dry film. The positive type photosensitive material in the form of a dry film is the most preferable material since a thick film of, for example, 10-100 .mu.m can be produced with the film thickness easily controlled, and its uniformity and handling properties are excellent.
As the positive type photosensitive material, there may be used, for example, materials comprising o-naphthoquinone diazides and alkali soluble phenolic resins, and materials comprising alkali soluble resins and substances capable of finally forming phenol by photolysis such as diazonium salts, for example, benzene diazonium salts. A specific example of a positive type photosensitive dry film that may be used is a film member composed of a polyester sheet and the above-mentioned positive type photosensitive material overlying the polyester sheet such as "OZATEC R 225" (the tradename of such a product manufactured by Hoechst Japan Co.).
The pattern layer 3 can be formed with a positive type photosensitive material 3a, as shown in FIG. 6A, using a so-called image forming process including exposure through a mask 7 to radiation at a wavelength h.nu., as illustrated in FIG. 6B. In this example, the pattern layer 3 may be produced such that a solvent-soluble polymer layer and a positive type photoresist layer of desired thicknesses are successively laminated on the substrate 1, and the pattern is formed in the positive type photoresist layer followed by selectively removing (developing) the solvent-soluble polymer layer as illustrated in FIG. 6C. As the solvent soluble polymer, there may be used any higher polymer compounds capable of forming a film by coating if there is a solvent which can dissolve the polymer. As the positive type photoresist, there may be used typically a positive type liquid photoresist comprising a novalac type phenolic resin and a naphtho-quinone diazide, and the like. As discussed above, a positive type photosensitive dry film is preferable from the standpoints of processing accuracy, easy removal and processability.
The substrate 1 having thereon the pattern layer 3 is then covered with an ink passage wall forming material as illustrated in FIGS. 3 and 6D. FIG. 3 is a schematic cross-sectional view at a position at or near section lines 2B--2B' in FIG. 2A, after the ink passage forming material 4 has been overlaid. As the ink passage wall forming material, there may be used preferably any material which can cover the abovementioned pattern layer. Since the material is to be a construction material constituting an ink jet recording head by forming ink passages, it is preferable to select a material having excellent mechanical strength, dimensional stability, corrosion resistance and adhesion to the substrate.
As such materials, there are used preferably liquid materials capable of being cured by heat and/or activating energy such as ultra-violet ray and electron beam. In particular, there are preferably used epoxy resins, acrylic resins, diglyco dialkyl carbonate resins, unsaturated polyester resins, polyurethane resins, polyimide resins, melamine resins, phenolic resins, urea resins and the like. In addition, there may be used metals capable of being laminated by electrolytic plating, vapor deposition, sputtering, or the like, for example, Cu, Ag, Au, Ni, Cr, Sn, Pb, Zn, Al, Ti and the like. In this example, it is preferable to use a curable liquid material as the ink passage wall forming material 4 from the standpoint of process efficiency.
When the above-mentioned curable liquid material is used as the ink passage wall forming material 4, the material is coated in a desired thickness on the substrate 1 by means of a known technique such as curtain coating, roll coating, spray coating, spin coating and the like. It is preferable to effect such coating after deaerating the material to avoid entrainment of air bubbles.
When the ink passage wall forming material 4 is in position as illustrated in FIGS. 3 and 6D, and the material is composed of the above-mentioned curable liquid material, curing is carried out under predetermined conditions in such a state that the liquid flow is suppressed; if desired, a pressing plate may be placed at the upper portion of the liquid material.
FIG. 4 is a schematic cross-sectional view showing the liquid material after curing for use as the ink passage wall forming material; the position of the cross section is similar to that of FIGS. 2B and 3. If curing is carried out at room temperature, the material is allowed to stand for 30 min. to 2 hours. If the curing is by application of ultraviolet radiation, irradiation for 10 min. or less at a wavelength h.nu. as illustrated in FIG. 6E can cure the material.
The most useful method for producing a cured ink passage wall forming member 4a is a curing method comprising curing epoxy resins with compounds, such as aromatic diazonium salts, aromatic onium salts and the like, capable of releasing a Lewis acid by application of an activation ray. After curing, the pattern layer is removed.
Though the manner of removing the pattern layer 3 is not restricted, it is preferable, for example, to soak the product illustrated in FIG. 4 in a liquid capable of dissolving and thereby removing the pattern layer 3. When removing the pattern layer 3, if desired, various techniques may be used for accelerating the removal such as ultrasonic treatment, spraying, heating, agitation and the like.
As the liquid used for removing the pattern layer, there can be used, for example, organic solvents (halogen-containing hydrocarbons, ketones, esters, aromatic hydrocarbons, ethers, alcohols, N-methylpyrrolidine, dimethylformamide, phenols and the like), water, aqueous solution of strong alkali (sodium hydroxide, kalium hydroxide and the like) and the like. If necessary, surfactants may be added to the abovementioned liquid. It is preferable to irradiate the pattern layer further with a light such as ultraviolet ray and the like. It is also preferable to heat the liquid to 40.degree.-60.degree. C.
FIGS. 5A and 6F show an example of an ink jet head in which the pattern layer 3 has been removed by dissolution. Ink supplying ports 6 are formed before the pattern layer 3 is removed by dissolution, and the pattern layer is removed. FIG. 5A is a schematic perspective view showing an ink jet recording head preform after the removal of the pattern layer. FIG. 5B is a schematic cross-sectional view at a position similar to that of FIGS. 2B, 3 and 4 after the removal of the pattern layer 3.
In this example, the pattern layer 3 is soaked in a liquid capable of dissolving the pattern layer 3, which is thereby dissolved and removed through ink supplying ports 6. The ink jet head preform shown in FIG. 5A, with fine ink passages 5a communicated with openings 5 and a common ink chamber 5b, is thus obtained.
The product illustrated in FIG. 5A may be cut along a dot and dash line C--C' before removing by dissolution so as to form discharge openings at a precise location. If desired, such cutting may be effected after forming the ink passage. Such cutting is effected mainly so as to get the optimum distance between the energy generating portion 2 of the energy generating body and the discharge opening. However, such cutting is not always necessary. If desired, the surface with the openings can be polished and smoothed for improved ink ejection.
The aforesaid method is effective to produce large quantities of reliable ink jet heads relatively easily. However, as the requirements for recording quality have become more stringent, the dimensional accuracy of the ink jet head, especially the ink passages, must be improved. From this viewpoint, it has turned out that the aforesaid method for producing an ink jet head, which heretofore had been sufficiently accurate, had some deficient aspects.
For example, a positive type photosensitive resin material including naphthoquinonediazo derivative is often used as the material for forming the pattern layer 3. The naphthoquinonediazo derivative has such strong absorbability of light for exposure in a range of a certain wavelength such as i ray, g ray or the like that there occurs lack of exposure of the aforesaid photosensitive resin material, especially a lower part of the resin material near the substrate 1. This is because the light for exposure decays in the aforesaid photosensitive resin material by absorption in the resin material itself. Therefore, it can sometimes be difficult to make a suitably shaped pattern in the aforesaid photosensitive resin material, especially when it is thick. Consequently, it can be difficult to obtain ink jet heads which meet high accuracy requirements for the ink passages (see FIG. 8B).